HP D5970A - NetServer - LCII Configuration Manual page 41

Chapter 4

Logical Drives, RAID Levels, and Array Spanning
On Worksheet B, logical drives are numbered LD0 through LD7. For each
logical drive you plan to create, record the following information:
Array number to which the logical drive is assigned
Whether the logical drive spans up to four sequentially-numbered arrays
RAID level
For each logical drive, you also need to define the logical drive size (capacity),
stripe size, write policy, read policy, and cache policy as defined in the sections
that follow.

Logical Drive Size
You can calculate the usable capacity to assign to each logical drive, or you can
let the HP NetRAID Assistant Wizard specify it during configuration. If you
calculate logical drive capacity, record it in Worksheet B.
If you want a logical drive to occupy less space than is available on one array,
you must enter the logical drive size.

Stripe Size (Stripe Depth)
Stripe size is the amount of data contiguously written to each disk in an array. It
is sometimes called "stripe depth." You can specify stripe sizes of 4 KB, 8 KB,
16 KB, 32 KB, 64 KB, and 128 KB for each logical drive. Consider the following
when setting your stripe size:
The default stripe size is 64 KB.
For best performance, choose a stripe size equal to or smaller than the
block size used by your operating system.
A large stripe size produces better performance if the system does mostly
sequential reads.
Choose a small stripe size if your system performs mostly random reads.
Online conversions of RAID 3 logical drives can be done only if the stripe
size is 64 KB.
For each logical drive, log the stripe size in Worksheet B.
NOTE Consider the stripe size carefully, because once the logical
drive is configured, you cannot change its stripe size.
Planning
35